American aid to the Russians.

When the war began in 1939 the United States was extremely suspicious of
Russian attitudes, and the attack on Finland brought American antipathy to
such a high level that a volunteer corps of Americans was formed to fight the
Russians. But when Hitler attacked Russia in the summer of 1941 the
American attitude changed overnight, and Russia became "our gallant ally."
Lend and lease to the Russians began in August 1941, four months before
the U.S. entered the war. By November 1941 President Roosevelt had
granted a loan of billion dollars to finance Lend Lease deliveries.
The amount of assistance kept growing. By the fall of 1942 the Americans
planned to deliver 4.5 million tons of supply to the Russians by the spring
of 1943.

American lend lease jeep in Stalingrad captured by the Germans

American policy toward Russia was far more open handed than British
policy. The British warned the Americans that Stalin would take over
all of Eastern Europe unless checked, but Roosevelt wanted Stalin to enter
the war against Japan, and to join the United Nations organization which
he believed would curb Russian ambitions.

Therefore American policy began to diverge sharply from British policy in
1943 and continued to diverge until the end of the war in Europe.
From the beginning of the attack on Russia, Stalin called for Allied
assistance and a second front  to be established in Western Europe to take
pressure of the Russians. Thereafter he was unremitting in his clamor for
that second front, and was unimpressed and ungrateful when the Americans
and British gave him his second front in North Africa, in the autumn of 1942.

Throughout the war Stalin and his officials kept pressing for more Allied
assistance, but told the Russian people virtually nothing about it. Still, the
appearance of American jeeps and trucks and aircraft could not be denied,
and the Russians people had a pretty good knowledge of the extent of
American an British assistance during the war.